1. Field of the Invention
The present invention relates to an apparatus and method for setting an identification signal, and more particularly to a setting apparatus and setting method for setting an identification signal to be added to a controller instruction value to estimate a parameter value used to functionally represent a characteristics change of a control object and which varies within a predetermined range.
2. Description of the Related Art
A type of setting apparatus for identification signals has been proposed in which an M-sequence signal is added during an automatic landing flight experiment (ALFLEX) of a HOPE scaled model to obtain aerodynamic characteristics data (for example, refer to xe2x80x9cAutomatic Landing Flight Experiment (ALFLEX) of a HOPE Scaled Modelxe2x80x9d, Japan Aerospace Association, January, 1998, Vol. 46, No. 528). An M-sequence (Maximum-length linear shift register sequence) signal is a pseudo-irregular signal that can be considered to approximate white noise and is one of the most well known and commonly used input signals for system identification.
However, this method of adding the M-sequence signals has an inherent problem in that identification accuracy and stability will not be constant with respect to time. Normally, because the input frequency component changes with time, there are times when the frequency component is within a region where the characteristics change of the control object is sharply reflected and times when the frequency component is within a region where the characteristics change of the control object is not reflected as sharply. When the input frequency component is at a frequency region where the characteristics change of the control object is sharply reflected, change becomes large and the identification accuracy improves, whereas the identification accuracy is reduced when the input frequency is at a frequency region where the characteristics change of the control object is not as sharply reflected. This problem becomes even more prominent when there is a disturbance.
One object of the present invention is to provide a setting apparatus for an identification signal that can accurately and stably identify a parameter representing a characteristics change of a control object without significantly affecting the output of the control object.
In order to solve the object mentioned above, the present invention employs the following.
According to one aspect of the present invention, there is provided a setting apparatus for an identification signal for setting an identification signal to be added to a controller instruction value to estimate a parameter value used to functionally represent a characteristics change of a control object and which varies in a predetermined range, said setting apparatus comprising frequency setting means for setting a frequency based on difference among gains when said parameter is sequentially varied within said predetermined range; amplitude setting means for setting an amplitude based on a variation width of the output of said control object; and signal setting means for setting said identification signal as a periodic signal with frequency set by said frequency setting means and amplitude set by said amplitude setting means.
With the setting apparatus for an identification signal according to the present invention, because the frequency is set by the frequency setting means based on the difference among the gains when the parameter is sequentially varied within a predetermined range, the frequency of the identification signal can be set to a frequency with high identification accuracy. As a result, identification can be performed with high accuracy. Moreover, because the amplitude is set by the amplitude setting means based on the variation width of the output of the control object, the output of the control object is not significantly affected.
According to another aspect of a setting apparatus for an identification signal of the present invention, the frequency setting means can be means for setting a frequency so that the difference in gain becomes larger. In this manner, the frequency of the identification signals can be set at a frequency where a characteristics change in the control object is sharply reflected, and thus identification can be more accurately performed.
According to another aspect of a setting apparatus of the present invention, said amplitude setting means can be means for setting an amplitude so that said variation width is less than or equal to a predetermined value. In this manner, the amplitude of the output of the control object can be maintained at a value less than or equal to the predetermined value. In this case, the predetermined value can be set at an allowed variation width for the output of the control object or at a value less than this value. In this manner, identification can be performed without significantly affecting the output of the control object.
According to another aspect of the present invention, said identification signal can be a periodic signal of square wave.
According to another aspect of the present invention, there is provided a setting method for an identification signal for setting an identification signal to be added to a controller instruction value to estimate a parameter value used to functionally represent a characteristics change of a control object and which varies within a predetermined range, said setting method comprising the steps of, (a) setting a frequency based on difference in gains when said parameter is sequentially varied within said predetermined range; (b) setting an amplitude based on a variation width of the output of said control object; and (c) setting said identification signal as a periodic signal having said set frequency and said set amplitude.
In this setting method for an identification signal according to the present invention, because the frequency is set based on the difference between gains when the parameter is sequentially varied within a predetermined range, the frequency of the identification signal can be set at a frequency of high identification accuracy. As a result, identification can be performed with high accuracy. Moreover, because the amplitude is set based on the variation width of the output of the control object, the output of the control object is not significantly affected.
According to another aspect of the present invention, in step (a) of the setting method of the identification signal, the frequency can be set at a frequency where said difference between gains becomes larger. In this manner, the frequency of the identification signal can be set at a frequency where the characteristics change in the control object is sharply reflected so that identification can be performed with a higher accuracy.
According to another aspect of the present invention, in step (b) of the setting method of the identification signal, the amplitude can be set so that said variation width is less than or equal to a predetermined value. In this manner, the amplitude of the output of the control object can be set to be less than or equal to a predetermined value. In this case, an allowed variation width of the output of the control object or a value less than this value can be used as the predetermined value. In this manner, identification can be performed without affecting the output of the control object.
According to another aspect of the present invention, in step (c) of the setting method of identification signals, the identification signal can be set as a periodic signal of square wave.